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This routine is part of the XTI interfaces which evolved from the TLI interfaces. XTI represents the future evolution of these interfaces. However, TLI interfaces are
supported for compatibility. When using a TLI routine that has the same name as an XTI routine, the tiuser.h header file must be used. Refer to the TLI COMPATIBILITY section for
a description of differences between the two interfaces. This function enables a transport user to request a connection to the specified destination transport user.
This function can only be issued in the T_IDLE state. The parameter fd identifies the local transport endpoint where communication will be established, while sndcall and rcvcall
point to a t_call structure which contains the following members:
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struct netbuf addr;
struct netbuf opt;
struct netbuf udata;
int sequence;
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The parameter sndcall specifies information needed by the transport provider to establish a connection and rcvcall specifies information that is associated with the newly established connection.
In sndcall, addr specifies the protocol address of the destination transport user, opt presents any protocol-specific information that might be needed by the transport provider, udata points
to optional user data that may be passed to the destination transport user during connection establishment, and sequence has no meaning for this function.
On return, in rcvcall, addr contains the protocol address associated with the responding transport endpoint, opt represents any protocol-specific information associated with the connection, udata
points to optional user data that may be returned by the destination transport user during connection establishment, and sequence has no meaning for this function.
The opt argument permits users to define the options that may be passed to the transport provider. The user may choose not to negotiate protocol options by setting the len field of opt to zero. In this case, the provider
uses the option values currently set for the communications endpoint.
If used, sndcall->opt.buf must point to a buffer with the corresponding options, and sndcall->opt.len must specify its length. The maxlen and buf fields of the netbuf
structure pointed by rcvcall->addr and rcvcall->opt must be set before the call.
The udata argument enables the caller to pass user data to the destination transport user and receive user data from the destination user during connection establishment. However, the amount of user data must not exceed the limits supported by the transport provider as
returned in the connect field of the info argument of t_open(3NSL) or t_getinfo(3NSL). If the len of udata is zero in sndcall, no data will be sent to the destination transport user.
On return, the addr, opt and udata fields of rcvcall will be updated to reflect values associated with the connection. Thus, the maxlen field of each argument must
be set before issuing this function to indicate the maximum size of the buffer for each. However, maxlen can be set to zero, in which case no information to this specific argument is given to the user on the return from t_connect(). If maxlen is greater than
zero and less than the length of the value, t_connect() fails with t_errno set to TBUFOVFLW. If rcvcall is set to NULL, no information at all is returned.
By default, t_connect() executes in synchronous mode, and will wait for the destination user's response before returning control to the local user. A successful return (that is, return value of zero) indicates that the requested connection has been established. However, if O_NONBLOCK is set by means of t_open(3NSL) or fcntl(2), t_connect() executes in asynchronous mode. In this case, the call will not wait for the remote user's response, but will return control immediately to the local user and return -1 with t_errno set to TNODATA
to indicate that the connection has not yet been established. In this way, the function simply initiates the connection establishment procedure by sending a connection request to the destination transport user. The t_rcvconnect(3NSL) function is used in conjunction with t_connect() to determine the status of the requested connection.
When a synchronous t_connect() call is interrupted by the arrival of a signal, the state of the corresponding transport endpoint is T_OUTCON, allowing a further call to either t_rcvconnect(3NSL), t_rcvdis(3NSL) or t_snddis(3NSL). When an asynchronous t_connect() call is interrupted by the arrival of a signal, the state of the corresponding transport endpoint is T_IDLE.
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